I have downloaded and tried to install Lcdproc-0.5.1-3 (wget a .deb package), which is the version needed to support IMON devices.But I'm stuck now, I also need to upgrade libusb, libncurses and libc6 to a newer unstable version, and can't find out howto...I'm used to Gentoo but Debian are another thing.

Is not wise to download and install deb packages not suited for debian sarge on pluto. My advice is for you to download the source and build it by hand on a pluto sytem using configure & make & make install.